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Discussion Starter · #1 ·
Hey everyone!

I just finished a major rebuild on my '02 Bird, and have been on two rides so far since. Unfortunately, I was not able to fix one of the issues I was having before the tear down: overheating.

When stuck at lights in the hot weather we're already having, the temp readout will climb over 250 F and start blinking. It also did this before the rebuild, but not when I originally got the bike (used to hang around 235 F). It has not boiled any coolant out. I am running Engine Ice also.

During the rebuild, I replaced the radiator, thermostat, and water pump. The new thermostat and water pump are OEM, and the latter was replaced as an assembly (the whole thing is new). I did not test the thermostat before putting it in, wishing I would have now :( the radiator is aftermarket from eBay but appears to be of good quality It has a slightly different bend in the filler neck which makes it possible to access the cap and siphon hoses through the opening in the lower right cowl.

I bled the air from the system. I had one test ride before I did this and realized my mistake as coolant was squirting out of the air bleed hole in the thermostat. I am 95% confident I got all the air out. I followed the procedure in the service manual, letting it warm up and blipping the throttle slightly, and as I was bleeding it I could see clearly when the liquid level would rise before burping out an air bubble, and it was no longer doing this when I finished.

The fan doesn't come on until about 220 F, which seems pretty hot. Would like to see it start around 190 F. But it does come on and appears to be functional, unless it just isn't spinning full speed.

I suppose I should pull the thermostat and test it to make sure it isn't stuck closed. Not looking forward to draining the coolant. The previous one failed this test which is why I replaced it.

Any other ideas or suggestions would be greatly appreciated!
 

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When you say "major rebuild" what else was done? Were any modifications made? Any parts replaced with 2nd hand or after market parts? (Apart from radiator of course) Or did you just do the work you describe?

If the thermostat test comes up OK, I'm thinking you still need to test for exhaust gas in the coolant, even though it may not be spitting out? That's all I got until we learn more.

It's a bummer to hear of it overheating after that much effort.
 

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Oh hang on a second, I don't see you talk about the radiator cap? Was that replaced? Should see the drama they can cause.
 

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Agree about the rad cap.
sammyscrap said:
I am 95% confident I got all the air out. I followed the procedure in the service manual,....
I initially followed the FSM (why wouldn't you!) and found I was still getting airlocks. Now after all coolant/rad changes I
1. use the FSM method and top up as much as possible
2. with the bike on the centre stand I run the bike up to temp shaking/squeezing the hoses as I go.
3. repeat 2 with the bike on the side stand and leave overnight ..... I've always managed to top up the rad when it cools and being on the side stand the rad neck is the 'high point' so the air finds its way there.

As a slightly 'curved ball' have you checked the 12v supply to the fan? I recently found an intermittent supply so the fan didn't always turn on / turned on when the temp was already too high.
 

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Discussion Starter · #6 ·
When you say "major rebuild" what else was done? Were any modifications made? Any parts replaced with 2nd hand or after market parts? (Apart from radiator of course) Or did you just do the work you describe?

If the thermostat test comes up OK, I'm thinking you still need to test for exhaust gas in the coolant, even though it may not be spitting out? That's all I got until we learn more.

It's a bummer to hear of it overheating after that much effort.
I put on a Yoshimura RS3 full system. But I don't think that's responsible since it was also overheating before the rebuild with the stock exhaust. The radiator cap is new and came with aftermarket radiator. I'm not sure what I should do to inspect it, but there is nothing obviously wrong with it. How does one test for exhaust gas in the coolant? I get a lot of action in the coolant when I rev the bike with the rad cap off, but I suspect that is just from the water pump doing it's job. I haven't run the thermostat test yet as I'm trying to exhaust all simple possibilities before draining the coolant. My new bodywork was a pain to get on and I'm not in a hurry to pull it back off :-(
 

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Discussion Starter · #7 ·
Agree about the rad cap.
I initially followed the FSM (why wouldn't you!) and found I was still getting airlocks. Now after all coolant/rad changes I
1. use the FSM method and top up as much as possible
2. with the bike on the centre stand I run the bike up to temp shaking/squeezing the hoses as I go.
3. repeat 2 with the bike on the side stand and leave overnight ..... I've always managed to top up the rad when it cools and being on the side stand the rad neck is the 'high point' so the air finds its way there.

As a slightly 'curved ball' have you checked the 12v supply to the fan? I recently found an intermittent supply so the fan didn't always turn on / turned on when the temp was already too high.
I just ran the bike up to temp on the side stand using your procedure, although I still have the bodywork on at the moment (holding out for a simple resolution, it was a pain getting it on last time) so I could only poke the two hoses going to/from the radiator in one spot each, and not the thermostat to water pump hose at all. I wasn't able to get any air out, but the coolant level did rise in the radiator to the point where some spilled over. The bodywork also appears to have put a slight kink in the siphon hose, since the new radiator has it positioned at a more outward angle (towards the plastics) than before.

I have the radiator cap off and I will let it sit until it cools and see where the level is at, but since I spilled some I should expect it to be lower.

I was watching the fan run last night and it appears to be going at a pretty good clip with low mechanical resistance, switched it off and it took at least 30 seconds to spin down to where the blades were individually visible again (not just a blur).

I was puttering along on my way home last night, about 30 mph in 2nd gear so probably about 3500-4000 RPM, and the temp went up from about 190 F to 210 F in the space of about 10 blocks. There were a few stop lights but even while moving I was observing an increase in temperature.
 

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To test for exhaust gasses in the coolant you need to get a "sniff" test done. This involves sucking the air in the expansion bottle through a coloured liquid, usually blue. If the liquid turns a greenish yellow Co2 is present. Most motorcycle or car workshops should be able to do this for you.
The link shows you how it's done.

https://www.youtube.com/watch?v=CCPMW84_zAcdone.
 

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I was puttering along on my way home last night, about 30 mph in 2nd gear so probably about 3500-4000 RPM, and the temp went up from about 190 F to 210 F in the space of about 10 blocks. There were a few stop lights but even while moving I was observing an increase in temperature.
Nothing wrong with that? Mine would do that and there is nothing wrong with it. Mine is in degrees C but on your scale my fan doesn't even come on until 218. In heavy traffic with frequent stops at lights etc mine goes up to 220, even 225 is in the healthy range.

You won't really see the temp go back down much until you sustain 50mph in clean air I.E. no other vehicle in front of you.
60 - 70mph in clean air it should start to drop and could go back down as low as 180 - 190 depending on the air temperature. on a stinking hot day here I've been doing 70mph on a freeway and still had it around 210.
 

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Put in a manual fan switch. Then you can control the temp by turning the fan on around 195/200 if your enter traffic at 35mph or less. I run my fan all the time in slow city traffic. Bike might get as hot as 210*. Easy fix just run a wire to the ground side of the fan to switch other leg to ground.
 
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Discussion Starter · #11 ·
Nothing wrong with that? Mine would do that and there is nothing wrong with it. Mine is in degrees C but on your scale my fan doesn't even come on until 218. In heavy traffic with frequent stops at lights etc mine goes up to 220, even 225 is in the healthy range.
OK, I guess I was just worrying about it since it had climbed over 250 during the day while in traffic, I thought maybe this was a sign that the coolant wasn't flowing through the radiator since it wasn't cooling down.
 

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Discussion Starter · #12 ·
Put in a manual fan switch. Then you can control the temp by turning the fan on around 195/200 if your enter traffic at 35mph or less. I run my fan all the time in slow city traffic. Bike might get as hot as 210*. Easy fix just run a wire to the ground side of the fan to switch other leg to ground.
Should that really be necessary to keep the bike from going into the red zone? I mean it was over 250 F while sitting in traffic, even after the fan comes on it continues to heat up and does not stabilize. I am worried that there is something wrong in the cooling system and that running the fan all the time would just be a workaround.
 

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Does it still get to 250?
I would regard 228 as a healthy maximum under most normal circumstances. If it's staying under that just ride it.
If it's getting over that get it tested for exhaust gas in the coolant
 

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Ideal coolant temperature? - LS1TECH

Read this thread yesterday after a city /highway ride in the first really warm temps this season, low to mid 80's.
I was surprised to see my normal highway temp of 185 F shoot up to 198F on the highway at 75 mph in heavy traffic
and then read teef's post about CLEAN air. As soon as I got away from the trucks it dropped back down in a few seconds.
When stopped in traffic I climb to about 218-220 and the fan controls it at that level. Same thing happened behind a slow
moving car on a back road in PA. They turned off and the temp dropped back down. Moral of story and note to self: Give the
vehicle in front of you as much space as possible. FWIW, I'm using Honda blue coolant this year. I was thinking about a new radiator
with the 30% improved cooling, but after reading the article I'm probably right where I should be. Thoughts? Sorry I have nothing
to add.
 

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Do you know how accurate your temp sensor or gauge is? It may not really be 250*. I don't like temps over 210*. The fan switch is a necessary if you want to keep stock motors from going over 210*+. It's your bike.
 

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Discussion Starter · #16 ·
Do you know how accurate your temp sensor or gauge is? It may not really be 250*. I don't like temps over 210*. The fan switch is a necessary if you want to keep stock motors from going over 210*+. It's your bike.
I'm not sure, it could just be a faulty temp gauge. Before I noticed this problem the first time, which was before all the work, I had a problem with the speedo acting weird, not showing proper speed and sitting at like 40 mph regardless of my actual speed. Then the next day the temp started to go way up. The speedo problem disappeared but since all the signals plug into the dash from below it could maybe be related. Anyone know a way to test this?
 

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Discussion Starter · #17 ·
Update!

So I brought the bike into a local shop to have them take a look at it. They ran it up to 255 F and didn't see any boiling over, which in their opinion indicated that the temp sensor or temp gauge are faulty and reading too high. Their logic makes sense to me - if it was actually that hot it should be boiling. I am using Engine Ice which may have a higher boiling point, but it is also true that I have never seen the system boil over even at higher readings (over 260 F).

However, they declined to work on the bike since I have an aftermarket radiator installed. That was disappointing to hear. So right now I think my strategy will be to replace the temp sensor. My bird is an 02, which I think means it is located on the thermostat? I am still a little confused about how the coolant temp sensor and fan work together. Can anyone give me a clue and talk about what it would take to swap the sensor out for a new one?

Thanks again guys!
 

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left of center suggestion.

Equip yourself with a heatgun/hairdryer and a thermometer.

Remove temp sensor and with it still connected blow some warm air over it then compare against the thermometer

(ok scrap that, you may find yourself with a puddle lol)

on an 02 the temp sensor sends a signal to the ECU and at a set temp that triggers a relay to engage the fan
 

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on an 02 the temp sensor sends a signal to the ECU and at a set temp that triggers a relay to engage the fan[/QUOTE]The manual states the ecu should start a 97 deg c but many don't start up till there well over 100 witch I think is to hot,
I've played around with the relays to see if I had a faulty relay and they all kicked the fan on at over 100c so that's got to be a fault in the ecu so I've over ridden that irregularitie with the manual switch
 

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Discussion Starter · #20 ·
So I've looked a little deeper into the service manual and found the procedure to remove the temp sensor. The worst part will be taking the lower plastics off and draining the coolant :( but I will use the opportunity to test the sensor with my ohmmeter and also give the new thermostat a test. Once those are both done I should have a better idea what is causing the problem. If neither of those two fail, I will have to start looking at the head gasket as the culprit (gulp).
 
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